This paper proposes a novel configuration of an elevated base station using an adaptive array for TDMA systems, which can simultaneously decrease the CCI (co-channel interference) and form a circular cell. The proposed base station comprises two sets of transceivers and antenna arrays, and an adaptive beam control unit. The transceivers work in different time slots. The circular cell that suppresses the interference is achieved by integrating the pattern control of the two antenna arrays. The effectiveness of the proposed base station configuration is evaluated by field measurements using an adaptive array testbed. We confirm that the proposed base station achieves a channel capacity that is approximately 30% greater than that of a base station employing an omni-directional antenna and generates an omni-zone with reduced CCI in an actual microcell system. Furthermore, we confirm by computer simulation that the proposed base station establishes a communicable area that is approximately 1.8 times larger than that of a base station employing an omni-directional antenna.

This paper proposes higher-order spread spectrum direct optical switching CDMA system and an aliasing canceler to remove the aliasing distortion caused by higher-order bandpass sampling. Theoretical analysis of the signal quality shows that the 3rd order bandpass sampling scheme can improve the carrier-to-interference-power ratio compared with the conventional 1st order bandpass sampling scheme, by 5 dB.

We study the joint optimization problem of a transmitter with multiple transmit antennas and a receiver with multiple receive antennas in a narrow-band communication system. We discuss the problem of designing a pre-filter at the transmitter, a post-filter at the receiver, and a bit allocation pattern to multiple symbols in the sense of minimizing the average bit error rate. With the optimized filters and the bit allocation, we could realize high efficiency and high data rate in band-limited channels.

This paper reports the implementation in three dimensions (3D) of diffusion models for low dose implanted dopants in silicon and the various numerical issues associated with it. In order to allow the end-users to choose between high accuracy or small calculation time, a conventional and 5-species diffusion models have been implemented in the 3D module DIFOX-3D belonging to the PROMPT plateform. By comparison with one and two-dimensional (1D and 2D) simulations performed with IMPACT-4, where calibrated models exist, the validity of this 3D models have been checked. Finally, the results obtained for a 3-dimensional simulation of a rapid thermal annealing step involved in the manufacturing of a MOS transistor are presented what show the capability of this module to handle the optimization of real devices.

This paper proposes a method for extracting subimages from a huge reference image by learning lifting wavelet filters. Lifting wavelet filters are biorthogonal wavelet filters containing free parameters developed by Sweldens. Our method is to learn such free parameters using some training subimages so as to vanish their high frequency components in the y- and x-directions. The learnt wavelet filters have the feature of training subimages. Applying such wavelet filters to the reference image, we can detect the locations where the high frequency components are almost the same as those of the target subimage.

This letter empirically evaluates the way how to calculate the complexity of methods, that is used in the definition of WMC(Weighted Method per Class), one of the Chidamber and Kemerer's metrics. With respect to the results of our experiment, Halstead's Software Science metric is the most appropriate one to evaluate the complexity of the methods.

An ultra low-noise and highly selective, experimental 2-GHz band cryogenic receiver front end (CRFE) has been newly developed for cellular base stations. It utilizes a high-Q superconducting filter, a very low noise cryogenic amplifier, and a highly reliable cooler that is very compact. Fundamental design of the CRFE is investigated. First, the equivalent noise temperature of the CRFE and the effect of improving CRFE sensitivity on base station reception are discussed. Next, essential technologies and fundamental characteristics of each component are described. Finally, influence of antenna noise, such as ground noise and man-made noise, is estimated through field tests both in urban and suburban areas.

We examine the detection of coded hybrid direct-sequence frequency-hopped spread-spectrum signals in the presence of narrowband interference. Since blind interference suppression requires a reliable estimate of the data, while at the same time data decoding requires interference suppression, we advocate an iterative ("turbo") detection scheme whereby information is exchanged between the interference suppressor and the soft-input soft-output decoder. Several suppression schemes are examined and compared. Simulation results show that this new scheme is robust, i.e., exhibits good performance under a modicum of assumptions on the interference structure. Turbo codes and convolutional codes are compared, showing that the former perform better.

As scaling has been continued more than 20 years, it has yielded faster and denser chips with ever increasing functionality. The scaling will continue down to or beyond 0.1 µm as proposed in SIA Technical Road map. With scaling, device performance improves, however, interconnect performance is degraded. In this scaled deep submicron technology, however, interconnects limit the performance, packing density and yield, if not properly modeled. In order to properly model and design the interconnect-dominated circuits, accurate and proper interconnect modeling is a must to assure the performance and functionality of ever-increasing complex multi-million transistor VLSI circuits. In this paper, the overall flow of interconnect modeling in IC design is reviewed including interconnect characterization, various 2-D/3-D field solvers, 2-D/3-D interconnect model library generation, and parameter extraction. And advanced topics of interconnect modeling in deep submicron are reviewed; statistical interconnect modeling.

Credit-based electronic payment systems are considered to play important roles in future automated payment systems. Like most other types of payment systems, however, credit-based systems proposed so far generally involve computationally expensive cryptographic operations. Such a relatively heavy computational load is preventing credit-based systems from being used in applications which require very fast processing. A typical example is admission-fee payment at the toll gate of an expressway without stopping a vehicle that travels at a high speed. In this article, we propose a very fast credit-based electronic payment protocol for admission-fee payment. More specifically, we propose a payment system between a high-speed vehicle and a toll gate which uses only very simple and fast computations. The proposed system makes use of an optimized Key Pre-distribution System (or KPS) to obtain high resistance against collusion attacks.

In this paper, a new set of difference equations is derived for transient analysis of the convergence of adaptive FIR filters using the Sign-Sign Algorithm with Gaussian reference input and additive Gaussian noise. The analysis is based on the assumption that the tap weights are jointly Gaussian distributed. Residual mean squared error after convergence and simpler approximate difference equations are further developed. Results of experiment exhibit good agreement between theoretically calculated convergence and that of simulation for a wide range of parameter values of adaptive filters.

This paper proposes a moment based encoding algorithm for iterated function system (IFS) coding of non-homogeneous fractal images with unequal probabilities. Moment based encoding algorithms for IFS coding of non-homogeneous fractal images require a solution of simultaneous algebraic equations that are difficult to handle with numerical root-finding methods. The proposed algorithm employs a variable elimination method using Grobner bases with floating-point coefficients in order to derive a numerically solvable equation with a single unknown. The algorithm also employs a varying associated-probabilities method for the purpose of decreasing the computational complexity of calculating Grobner bases. Experimental results show that the average computation time for encoding a non-homogeneous fractal image of 256256 pixels and 256 gray levels is about 200 seconds on a PC with a 400 MHz AMD K6-III processor.

In this letter, we remark a well-known nonlinear filtering technique realize immediate effect to suppress the influence of the additive measurement noise in the input to a set theoretic linear blind deconvolution scheme. Numerical examples show ε-separating nonlinear pre-filtering techniques work suitably to this noisy blind deconvolution problem.

The blind separation of sources is a recent and important problem in signal processing. Since 1984, it has been studied by many authors whilst many algorithms have been proposed. In this paper, the description of the problem, its assumptions, its currently applications and some algorithms and ideas are discussed.

In this paper, we present our work on the design of a new FPGA architecture targeted for high-performance bit-serial pipeline datapath. Bit-parallel systems require large amount of routing resource which is especially critical in using FPGAs. Their device utilization and operation frequency become low because of large routing penalty. Whereas bit-serial circuits are very efficient in routing, therefore are able to achieve a very high logic utilization. Our proposed FPGA architecture is designed taking into account the structure of bit-serial circuits to optimize the logic and routing architecture. Our FPGA guarantees near 100% logic utilization with a straightforward place and route tool due to high routability of bit-serial circuits and simple routing interconnect architecture. The FPGA chip core which we designed consists of around 200k transistors on 3.5 mm square substrate using 0.5 µm 2-metal CMOS process technology.

This paper reports a Monte Carlo calculation of the bimolecular reaction of arsenic precipitation. As the accuracy of the numerical solution for the coupled rate equations strongly depends on the size of grid spacing, it is necessary to choose adequate number of rate equations in order to understand the behavior of the extended defects. Therefore, we developed a general kinetic Monte Carlo model for the extended defects, which explicitly takes the time evolution of the size density of the extended defects into account. The Monte Carlo calculation exhibits a quantitative agreement with the experimental data for deactivation, and successfully reproduces the rapid deactivation at the beginning phase followed by slow deactivation in the subsequent steps.

This paper presents an efficient public-key protocol for mutual authentication and key exchange designed for mobile information services in UMTS. Certain modifications to the ASPeCT registration protocol is proposed to introduce Temporary Mobile User Certificate in UMTS environments. Proposed Temporary Mobile User Certificate, digitally-signed by the private signing key of the TTP located in the user's visiting domain, will be issued to the user during the registration protocol. ASPeCT AIP protocol can be modified to reduce communication overhead and speed up verification process using Temporary Mobile User Certificate between the user and the Value-Added Service Provider (VASP) located in the user's visiting domain. Furthermore, Temporary Mobile User Certificate can provide anonymity for a mobile user during the ASPeCT AIP protocol.

This paper newly proposes radio-over-fiber systems using cascaded radio-to-optic direct conversion (ROC) scheme. The ROC system can convert a radio signal into an optical signal with the same signal format. The received carrier-to-noise ratio (CNR) performance of the radio-over-fiber systems using the ROC/heterodyne detection (HD) scheme and the ROC/self-heterodyne detection (SHD) scheme are theoretically analyzed. The optimization of an optical modulation index (OMI) in each radio base station (RBS) is also presented. By using the proposed OMI optimization method, the ROC/HD and the ROC/SHD schemes are shown to provide approximately 16 dB and 14 dB improvement over the intensity modulation/direct detection scheme when the number of RBS is 20 and the radio-frequency (RF) signal bandwidth is 150 MHz, respectively. The ROC/SHD scheme enables a receiver structure to become simple while still achieving high received CNR.

In this paper, performance of a PN code acquisition scheme is analyzed and simulated for a DS/CDMA overlay system where a CDMA user and a narrowband user coexist in the same frequency band. A narrowband user is modelled as a narrowband interference (NBI) located at the fraction of a CDMA user's bandwidth. To suppress the NBI, an interference suppression filter is employed at the receiver frontend. Acquisition performance is evaluated in terms of mean acquisition time using state transition diagram for acquisition process. To apply for a DS/CDMA mobile cellular environments, multiple access interference and imperfection of power control are taken into account in the analysis of acquisition performance. The imperfect power control is considered by modelling the power of each user to be lognormally distributed about nominal received power. From the simulation results, it is shown that for the cases of perfect and imperfect power control, the interference suppression filter is very effective for supprssion of the NBI and rapid PN code acquisition in a DS/CDMA overlay environment. It is also shown that the one-sided tap number of 5 for interference suppression filter is sufficient to suppress the NBI. And, capacity estimates are compared based on acquisition and BER performance. The analysis in this paper can be applied to the practical situations for a DS/CDMA overlay environment.

The classical algebraic modelling approach for integer programming (IP) is not suitable for some real world IP problems, since the algebraic formulations allow only for the description of mathematical relations, not logical relations. In this paper, we present a language + for IP, in which we write logical specification of an IP problem. + is a language based on the predicate logic, but is extended with meta predicates such as at_least(m,S), where m is a non-negative integer, meaning that at least m predicates in the set S of formulas hold. The meta predicates facilitate reasoning about a model of an IP problem rigorously and logically. + is executable in the sense that formulas in + are mechanically translated into a set of mathematical formulas, called IP formulas, which most of existing IP solvers accept. We give a systematic method for translating formulas in + to IP formulas. The translation is rigorously defined, verified and implemented in Mathematica 3.0. Our work follows the approach of McKinnon and Williams, and elaborated the language in that (1) it is rigorously defined, (2) transformation to IP formulas is more optimised and verified, and (3) the transformation is completely given in Mathematica 3.0 and is integrated into IP solving environment as a tool for IP.